i got a new goldfish the other day, and he was labeled as a ryukin, but on closer examination, i'm not 100% sure. he has the round belly, but no hump, and his finnage, face and rear section look a lot more like a shubunkin (he's not long and sleek like a shubunkin though, and has paired caudals) is he maybe a mixed breed, or something else entirely? i'll post a photo later, but he's beautiful nonetheless.

Ryukins develop their shape over time. I have two, my first one didn't look like any particular breed when I got him. Now he has blossoming in to a beautiful Ry, his hump is growing nicely, his tummy is plump. He's perfect.